The present invention is directed toward an airlift pump, and more particularly, to an airlift having multiple stages and using only one air source for elevating liquids.
Multiple stage airlifts have been used to elevate liquids to a higher level by using air pressure. As is well known in the art, air is usually pumped into a lower level of the airlift where the liquid has accumulated and is at rest. A pump is typically provided which pumps air under pressure into the airlift for moving the liquid. From a general standpoint, it is frequently the case in multiple stage airlifts that a plurality of air sources are used so as to initiate the lift at each level. Accordingly, when a lower stage of the airlift moves the liquid up into the next stage, the second source of air pressure takes over and moves the same liquid through that stage and this process continues until the liquid is moved through each stage and to its destination.
There also exist airlifts which use a single source of air pressure at the lowest portion of the multiple stage airlift. With these systems, air is forced into the liquid or the like and the bubbles formed in the liquid tend to move the same upward. At each stage, there usually exists an accumulation device or structure which catches and maintains the water from the lower stage in the second stage. The air from the same source then repeats this process at the next stage. However, these systems require the lift to be submerged a distance equal to the lifting elevation. The prior art discloses both of these types of multiple stage airlifts.
U.S. Pat. No. 1,339,137 to Rogers, for example, discloses an airlift apparatus comprised of an upper and a lower lift connected at a central fluid collection chamber. Fluid is moved via pressurized air bubbling up through the same and carrying it upwardly. Because of slippage and lost work due to the effects of air bubbles increasing in size as they move upwardly, the upper and lower lifts are formed in lengths allowing only minimal loss. Similarly, perforations are formed in the ends of the lifts for maintaining the bubbles in a more productive smaller diameter state. A single source air supply is used which is regenerated in the chamber. Unlike the instant invention, however, the device is limited to raising the fluid a distance equal to the distance that the lower lift is submerged.
U.S. Pat. No. 1,374,952 also to Rogers discloses a different type of multiple stage airlift apparatus. This apparatus includes several cylindrical stages interconnected at their ends by regenerator devices. Each regenerator device functions to change the columns of large bubbles and water into columns of smaller bubbles and water so as to reduce slippage of the air bubbles upwardly in the column and reduce the lost work associated therewith. The regenerator itself does not function to store any of the water at the different stages, it only functions to form smaller bubbles. In addition, the airlift apparatus in Rogers must be submerged a distance equal to the distance of the same above the water. Therefore, the airlift apparatus is limited in its lifting height by the depth of the water.
U.S. Pat. No. 3,718,407 to Newbrough discloses a multi-stage gas lift fluid pump system. The system utilizes high pressure gas delivered from a pump into the submerged end of a cylindrical enclosure. The pumped in gas is used to lift oil from a producing zone within the ground upward and outward into an above ground storage tank. The multi-stage lift is comprised also of supplemental lift devices positioned at intervals along the vertical length of the cylindrical enclosure. Each supplemental lift device includes a check valve which has the effect of reducing the total head of fluid which each section is called upon to lift. The fluid or oil is raised stage by stage until it reaches the surface where it is stored and the gas used to lift the same is removed and used again to lift more of the oil. The supplemental lift devices use a nozzle-type arrangement wherein the gas is forced therethrough creating a Bernoulli effect wherein a low pressure zone is formed above the oil, thereby causing the same to flow upward. The Newbrough device does not use air bubbles for moving the fluid.